Connecting rod for a turbine engine, with an integrated filter, and production method thereof

ABSTRACT

A connecting rod, in particular for a turbine engine, includes an intermediate body with a general elongated shape. Connecting heads may be located at the longitudinal ends of the elongated shape, which may include holes having axes that are, for example, substantially parallel. The connecting rod is characterized in that the heads are assembled or formed as a single piece with at least one part of the body. At least one of the heads includes an alveolar annular part, about the axis of the hole, forming a vibrating filter and having a flexural and/or compressive deformation capacity greater than that of the rest of the connecting rod and, in particular, that of the body.

TECHNICAL FIELD

The present invention concerns a connecting rod, in particular of a turbomachine, as well as a method for producing such a connecting rod.

BACKGROUND

The state of the art includes patent applications published under the numbers US-A1-2016/167132 and US-A1-2016/245710.

A turbomachine, such as a turbojet engine, used for aircraft propulsion comprises auxiliary machines necessary for its operation. Examples include fluid pumps for actuating control, lubrication or fuel members as well as electrical generators. These machines are mechanically mounted with a gearbox which is itself connected to a shaft of the engine by a suitable mechanical connection. This box is commonly referred to by its acronym, AGB (Accessory Gear Box), in this field. The gearbox is kept suspended on the engine casing by suspension devices comprising connecting rods.

A connecting rod comprises an intermediate body of generally elongated shape and connected at its longitudinal ends to connecting heads comprising orifices whose axes are in substantially parallel planes.

FIG. 1 shows a connecting rod 10 of this type, the section plane passing through the axis of one of the above-mentioned orifices 12. This orifice 12 receives an externally cylindrical cage 14, which is held by crimping in the orifice 12. The inner surface of the cage 14 serves as a guide for a sleeve with a spherical outer surface forming a ball joint 16.

Each head 18 of the connecting rod is mounted between the ears 20, 22 of a female clevis 24, only a part of the connecting rod 10 being visible in FIG. 1. The visible head 18 is held between the two ears 20, 22 by a screw 26 which passes through the latter and the ball joint 16. The screw 26 is itself secured by a nut 28. The connecting rod 10 is axially fixed in the direction of the screw 26 by the ball joint 16 which, as shown in the figure, is supported on each side against a bearing 30 inserted in the orifice of each ear 20,22. Thanks to this ball joint assembly, the head 18 can rotate freely around the axis of the screw and around any axis perpendicular to the screw axis within the limits of the stops defined by the environment. The movement is limited based on the interval, arranged on either side, between the connecting rod head 18 and the ears 20, 22 of the clevis 24.

During its service life, this connection is subjected to micro-displacements due especially to vibration forces, in particular stresses oriented parallel to the axis of the connecting rod 10, due especially to the slight inclination of the connecting rods 10 with respect to the horizontal plane. These stresses eventually wear out and degrade the suspension device.

One solution to this problem is to equip this type of device with vibration damping means. The solution illustrated in FIG. 1 consists of mounting the screw 26 in the orifices in the ears 20, 22 of the clevis via damper bearings 30. The orifice of each ear receives a damper bearing 30 comprising inner 34 and outer 36 rings between which extends an elastomeric annular damper 38.

However, this technology has disadvantages related, in particular, to the temperature resistance and to liquid products (pollutants, solvents, kerosene, etc.) of the damper (elastomer degradation and variability in dynamic behaviour). Indeed, due to its elastomer construction, the use of the damper is limited in applications where the ambient temperature is generally lower than 200° C. In addition, the failure mechanisms of elastomers are poorly formalized, which implies a high frequency of replacement of the bearing for replacement as soon as the first crack appears, whereas it should still be able to perform its function for many cycles.

FIG. 2 illustrates another solution to the above-mentioned problem, which is described in patent FR-B1-2 866 683. The solution is to provide an elastomeric damper 40 on the head 18 of the connecting rod 10.

However, this damper has the same disadvantages as the previous solution. In addition, the use of an elastomer damper, and more precisely a damper made of insulating material, breaks the electrical continuity between the suspended equipment, for example the connecting rod and the head of the connecting rod comprising the elastomer damper, and the support assembly, for example the motor casing and the gearbox.

To ensure electrical continuity between the suspended equipment and the support assembly when the damper is made of elastomer, a metal braid is generally added to connect the suspended equipment and the support assembly.

However, the metal braid, for example in stainless steel, is fragile and expensive. In addition, the attachment of a metal braid increases the mass of the suspended equipment and makes it more complex. Indeed, the attachment of a metal braid to the suspended equipment and to the support assembly requires screws or studs or inserts, washers, nuts and resist layers (i.e. masks) in the corrosion protection of the suspended equipment to allow electrical continuity.

DISCLOSURE OF THE INVENTION

This invention proposes an improvement of the technology described above, which represents a simple, effective and economical solution, in particular to address the above-mentioned thermal resistance problem of the damping means.

The invention proposes a connecting rod, in particular for a turbomachine, comprising an intermediate body of generally elongated shape and connected at its longitudinal ends to connecting heads comprising orifices whose axes are for example substantially parallel, characterized in that said heads are assembled or integrally formed with at least one part of said body and at least one of them comprises, about the axis of its orifice, an alveolar annular part forming a vibratory filter and having a flexural and/or compressive deformation capacity greater than that of the rest of the connecting rod and in particular that of said body.

The filter or a part of the connecting rod can thus be made of a material resistant to high temperatures, for example above 200° C. This is made possible by the alveolar structure having flexibility properties and in particular deformation capacities in a flexural and/or compressive deformation sufficient to filter a vibration spectrum to which the suspended system is likely to be exposed during operation.

The connecting rod according to the invention is at least partly metallic.

According to an embodiment, when the connecting heads are integrally formed with at least one part of the body of the connecting rod, the connecting rod is metallic.

According to an embodiment, when the connecting heads are assembled with at least one part of the body of the connecting rod, the connecting rod is at least partly metallic. In this case, the connecting rod can be partly metallic and partly made of composite material. In particular, at least one part of the connecting heads and at least one part of the body of the connecting rod are metallic. Preferably, the body of the connecting rod and the alveolar annular part of at least one of the connecting heads of the connecting rod are at least partly metallic.

Advantageously, such a connecting rod allows to combine a damped connection function, in particular thanks to the alveolar annular part, and an electrical continuity function, in particular thanks to the composition of the connecting rod, which is at least partly metallic.

The heads assembled with at least one part of the body of the connecting rod, at least one of them comprising an alveolar annular part, at least one part of the connecting heads and at least one part of the body being metallic, allows to ensure electrical continuity at the alveolar annular part between the connecting rod, the AGB and the motor casing.

Thus, the connecting rod according to the invention allows advantageously to combine two specific functions, a damped connection function and an electrical continuity function, in the same element, in this case the connecting rod.

In addition, the connecting rod according to the invention, avoids the use of a metal braid, which is fragile, expensive and increases the mass of the suspended equipment. As a result, the mass of the connecting rod according to the invention is reduced compared to the mass of the connecting rods according to the prior art, thanks to the removal of the metal braid and the fixing elements of the latter.

This also simplifies the suspended equipment to be connected, for example an AGB. Indeed, with a connecting rod according to the invention, there is no longer any need to use fixing points or resist layers in the corrosion protection of the suspended equipment to allow the electrical continuity.

Advantageously, the connecting rod according to the invention has a high electrical conductivity compared to that of a connecting rod according to the prior art. Preferably, the electrical conductance of the connecting rod is greater than or equal to 200 Siemens (S). More preferably, the electrical conductance of the connecting rod is greater than or equal to 400 S.

Preferably, the connecting rod according to the invention has a low electrical resistance compared to that of a connecting rod according to the prior art. Preferably, the electrical resistance of the connecting rod is less than or equal to 5 mΩ. More preferably, the electrical resistance of the connecting rod is less than or equal to 2.5 mΩ.

The connecting rod, according to invention, may include one or more of the following characteristics, taken in isolation from each other or in combination with each other:

-   -   said annular part comprises a lattice-shaped structure,     -   said body comprises an alveolar longitudinal part, and     -   said longitudinal part comprises a lattice-shaped structure.

This invention also concerns a suspension device, in particular for a turbomachine, comprising a connecting rod as described above, this device further comprising an assembly comprising a ball joint and a cage which surrounds the ball joint and is shrunk or fixed in the orifice of the connecting rod head which comprises said annular part.

The invention also concerns a turbomachine, in particular an aircraft turbomachine, comprising such a connecting rod or such a device, in particular for suspending an AGB to an engine casing.

The electrical continuity function allows grounding, and therefore equipotentiality, between the connecting heads and the body of the connecting rod, the motor casing and the AGB.

Finally, the invention concerns a method for producing a connecting rod, or a connecting rod part, as described above, characterized in that it comprises a step of additive manufacturing of the connecting rod, and in particular of its alveolar annular part, for example by selective melting of powder beds.

The heads integrally formed with at least one part of the body of the connecting rod by metal additive manufacturing, at least one of which comprises an alveolar annular part, allows to ensure electrical continuity at the alveolar annular part between the connecting rod, the AGB and the motor casing.

The filter function, described here in the annular part, can be installed either in the connecting rod or in ears of a female clevis.

DESCRIPTION OF THE FIGURES

The invention will be better understood and other details, characteristics and advantages of the invention will appear more clearly when reading the following description by way of non-limiting example and by reference to the annexed drawings in which:

FIG. 1 is a schematic cross-sectional view of a particular model of a connecting rod connected to a clevis, according to an art prior to the present invention,

FIG. 2 is a schematic cross-sectional view of a connecting rod model connected to a clevis, according to another art prior to the present invention,

FIG. 3 is a very schematic partial view of a connecting rod model according to the invention,

FIG. 4 is a schematic cross-sectional view of the connecting rod of FIG. 3 connected to a clevis,

FIG. 5 is a cross-sectional schematic view of a plain bearing for connecting rod, and

FIG. 6 is, for example, a very schematic view of an installation for the additive manufacturing of a connecting rod or connecting rod part, in this case according to FIG. 3.

DETAILED DESCRIPTION

A connecting rod 100 according to the invention, as illustrated in FIG. 3, comprises an intermediate body 102 of generally elongated shape and connected at its longitudinal ends to connecting heads 104 comprising orifices 106 whose axes A are for example substantially parallel. The connecting rod 100 can be at least partly metallic. Only a part of the connecting rod 100 is visible in the drawing.

The heads 104 can be integrally formed with the body 102 or a part of the body. Preferably, the connecting rod 100 is made of metal and by additive manufacturing, as described in more detail in reference to FIG. 6.

The heads 104 can be assembled with the body 102 or a part of the body. The connecting rod 100 can be partly metallic and partly made of composite material. More precisely, at least a part of the heads 104 and at least a part of the body 102 are metallic. The heads 104 and the body 102 are shaped so that the metal parts of said heads 104 and said body 102 provide electrical continuity along the connecting rod 100, i.e. between the two heads 104 and along the body 102. Thus, the heads 104 and the body 102 are shaped so that the metal parts of said heads 104 and of said body 102 provide electrical continuity between the elements to which the connecting rod is connected.

Preferably, the connecting rod 100 has a high electrical conductivity. The electrical conductivity of the connecting rod 100 can be greater than or equal to 200 S, i.e. greater than or equal to 200 A·V⁻¹. Preferably the electrical conductivity of the connecting rod 100 is greater than or equal to 400 S, i.e. greater than or equal to 400 A·V⁻¹.

The connecting rod 100 preferably has a low electrical resistance. The electrical resistance of the connecting rod 100 can be less than or equal to 5 mΩ, i.e. less than or equal to 5·10⁻³ V·A⁻¹. Preferably the electrical resistance of the connecting rod 100 is less than or equal to 2.5 mΩ, i.e. less than or equal to 2.5·10⁻³ V·A⁻¹.

At least one of the heads 104 comprises, about the axis of its orifice, an alveolar annular part 108 forming a vibration filter and having a flexural and/or compressive deformation capacity greater than that of the rest of the connecting rod and in particular that of the body 102.

The alveolar annular part 108 is at least partly metallic. Advantageously, the alveolar annular part 108 is entirely metallic.

This annular part 108 preferably comprises a lattice-shaped structure, formed by a three-dimensional set of patterns (such as interlocking bars) linked to each other. These patterns are separated and spaced from each other by spaces that form the cells of the part 108.

Advantageously, the body 102 of this connecting rod comprises an alveolar longitudinal part 110, which can have the same type of structure, i.e. in a lattice shape. As mentioned above, the part 108 has a higher flexural and/or compressive deformation capacity than the part 110. The alveolar or lattice structure of the part 110 allows in particular to lighten it and/or reinforce the constrained areas.

The connecting rod 100 can be combined with an assembly comprising a ball joint 112 and a cage 111 to form a suspension device (FIGS. 3 and 4). The cage 111, which surrounds the ball joint 112, is shrunk or fixed by another method in the orifice 106 of the connecting rod head 104 which comprises said annular part 108. As shown in FIG. 4, if the vibratory filter formed by the part 108 is integrated with the connecting rod 100, then it is no longer necessary to provide damping bearings in the orifices 114 of the ears 116 of the clevis, which can only receive simple guiding cylindrical sleeves 118. These sleeves 118 and the ball joint 112 are traversed by a screw 120 like that of FIG. 1.

FIG. 5 illustrates a variant of embodiment of the invention in which the part 108, the cage 111 and the ball joint 112 of the preceding embodiment are replaced by a plain bearing 119 with integrated vibratory filter. The bearing 119 comprises two annular rings, respectively inner 119 a and outer 119 b, extending around each other and connected together by an alveolar or lattice structure 119 c forming the vibratory filter due to its higher flexural and/or compressive deformation capacity than the rings. The bearing is preferably integrally formed. The rings 119 a and 119 are thus connected to each other in a monobloc way by the structure 119 c which can comprise arms organized in repeated and ordered geometric patterns. The whole is preferably metallic. The bearing 119 can also be integrally formed with a connecting rod, or it can be provided and fixed in a connecting rod orifice.

The connecting rod 100 is advantageously manufactured by additive manufacturing. FIG. 6 shows an example of an installation for producing a connecting rod by additive manufacturing, and in particular by selective melting of powder beds via a high energy beam.

The machine includes a feeder tray 170 containing powder of a material such as a metal alloy, a roller 130 to transfer this powder from this tray 170 and spread a first layer 110 of this powder on a construction support 180.

The machine also comprises a recycling bin 140 to recover the used powder (especially unfused or non-sintered powder) and the excess powder (mostly), after spreading the powder layer on the construction support 180. Thus, most of the powder in the recycling bin is new powder. Also, this recycling bin 140 is commonly referred to by the profession as an overflow bin or ashtray.

This machine also includes an energy beam generator 190 (e.g. laser) 195, and a control system 150 capable of directing this beam 195 to any region of the construction support 180 to scan any region with a powder layer. The shaping of the energy beam (laser) and the variation of its diameter on the focal plane are done respectively by means of a beam dilator 152 and a focusing system 154, the whole constituting the optical system.

This machine, to apply the method similar to a Direct Metal Deposition or DMD method to a powder, can use any high-energy beam in place of the laser beam 195, as long as this beam is sufficiently energetic to in the first case melt or in the other case form collars or bridges between the powder particles and a part of the material on which the particles rest.

The roller 130 can be replaced by another suitable dispensing system, such as a dispenser (or hopper) combined with a scraper blade, a knife or a brush, suitable for transferring and spreading the powder in layer.

The control system 150 comprises, for example, at least one steerable mirror 155 on which the laser beam 195 is reflected before reaching a powder layer of which each point of the surface is always located at the same height with respect to the focusing lens, contained in the focusing system 154, the angular position of this mirror 155 being controlled by a galvanometric head so that the laser beam scans at least a region of the first powder layer, and thus follows a pre-established component profile.

This machine works as follows. A first layer 110 of powder of a material is applied to the construction support 180 by means of the roller 130, this powder being transferred from a feeder tray 170 during a forward movement of the roller 130 and then scraped, and possibly slightly compacted, during one (or more) return movement(s) of the roller 130. The excess powder is recovered in the recycling bin 140. A region of this first layer 110 of powder, by scanning with the laser beam 195, is heated to a temperature higher than the melting temperature of this powder (liquidus temperature). The galvanometric head is controlled according to the information contained in the database of the computer tool used for the computer-aided design and manufacture of the component to be manufactured. Thus, the powder particles 160 of this region of the first layer 110 are melted and form a first cord 115 in one part, integral with the construction support 180. At this stage, several regions independent of this first layer can also be scanned with the laser beam to form, after melting and solidifying the material, several first cords 115 separated from each other. The support 180 is lowered by a height corresponding to the already defined thickness of the first layer (between 20 and 100 μm and generally 30 to 50 μm). The thickness of the powder layer to be fused or consolidated remains a variable value from one layer to another because it is highly dependent on the porosity of the powder bed and its flatness, while the pre-programmed displacement of the support 180 is an invariable value within a clearance. A second layer 120 of powder is then applied to the first layer 110 and to this first cord 115, and then a region of the second layer 120 which is located partially or completely above this first cord 115 is heated by exposure to the laser beam 195, so that the powder particles of this region of the second layer 120 are melted, with at least one part of the first cord 115, and form a second cord in one part or consolidated 125, all of these two cords 115 and 125 forming a block in one part. For this purpose, the second cord 125 is advantageously already fully bonded as soon as a part of this second cord 125 is bonded to the first element 115. It is understood that depending on the profile of the component to be manufactured, and in particular in the case of an undercut surface, the above-mentioned region of the first layer 110 may not lie, even partially, below the above-mentioned region of the second layer 120, so that in this case the first cord 115 and the second cord 125 do not then form a block in one part. This method of manufacturing the component layer by layer is then continued by adding additional layers of powder on the already formed assembly. Scanning with the beam 195 allows each layer to be manufactured by giving it a shape in accordance with the geometry of the component to be produced, for example the above-mentioned lattice structures. The lower layers of the component cool more or less quickly as the upper layers of the component are manufactured.

In order to reduce the contamination of the component, for example, with dissolved oxygen, oxide(s) or another pollutant during its manufacturing layer by layer as described above, this manufacturing must be carried out in an enclosure with a controlled degree of hygrometry and adapted to the method/material pair, filled with a neutral gas (not reactive) with regard to the material in question such as nitrogen (N₂), argon (Ar) or helium (He) with or without addition of a small quantity of hydrogen (H₂) known for its reducing capacity. A mixture of at least two of these gases can also be considered. To prevent contamination, particularly by oxygen from the surrounding environment, it is customary to overpressure this enclosure.

Thus, selective melting or selective laser sintering allows to manufacture low-polluted components with good dimensional accuracy, whose three-dimensional geometry can be complex.

Selective melting or selective laser sintering also preferably uses powders of spherical morphology, clean (i.e. not contaminated by residual elements from the synthesis), very fine (the size of each particle is between 1 and 100 μm and preferably between 45 and 90 μm), which allows to obtain an excellent surface state of the finished component.

Selective melting or selective laser sintering also reduces manufacturing times, costs and fixed costs compared to a moulded, injected or machined from a single piece component. 

1. A connecting rod for a turbomachine, comprising an elongated intermediate body and connected at longitudinal ends to connecting heads, wherein the connecting heads include orifices with substantially parallel axes, wherein said heads are either assembled or integrally formed with at least one part of said body and at least one of said heads comprises an alveolar annular part about the axis of the orifice of said at least one head, wherein said alveolar annular part forms a vibratory filter and said alveolar annular part has at least one of a flexural and a compressive deformation capacity greater than a remaining portion of the connecting rod.
 2. The connecting rod according to claim 1, wherein the connecting rod is at least partially metallic.
 3. The connecting rod according to claim 2, wherein said body and said heads are partially metallic.
 4. The connecting rod according to claim 2, wherein an electrical resistance of the connecting rod is less than or equal to 5 mΩ.
 5. The connecting rod according to claim 2, wherein electrical conductance of the connecting rod is greater than or equal to 200 S.
 6. The connecting rod according to claim 1, wherein said alveolar annular part comprises a lattice-shaped structure.
 7. The connecting rod according to claim 1, wherein said body comprises an alveolar longitudinal part.
 8. The connecting rod according to claim 7, wherein said longitudinal part comprises a lattice-shaped structure.
 9. A suspension device for a turbomachine, comprising a connecting rod according to claim 1, the suspension device further comprising an assembly comprising a ball joint and a cage that surrounds the ball joint and is located in the orifice of the connecting head that comprises said annular part.
 10. A method for producing a connecting rod according to claim 1, wherein the method comprises a step of additive manufacturing of the connecting rod.
 11. The method of claim 10, wherein the additive manufacturing includes selective melting of powder beds.
 12. The method of claim 10, wherein the method further comprises a step of additive manufacturing of the alveolar annular part.
 13. The connecting rod according to claim 2, wherein the alveolar annular part of one of the heads is partially metallic.
 14. The connecting rod according to claim 2, wherein an electrical resistance of the connecting rod is less than or equal to 2.5 mΩ.
 15. The connecting rod according to claim 2, wherein an electrical conductance of the connecting rod is greater than or equal to 400 S. 